Heretofore, a zirconia single crystal i.e. so-called cubic zirconia has been used for applications to decorations and applications to jewelry. Further, cubic zirconia colored by adding a coloring agent such as a transition metal or a rare earth element is also used for the same applications (Non-Patent Document 1).
To prepare such cubic zirconia, it is necessary to prepare a bulk zirconia single crystal e.g. by skull melting process first, and then to process the prepared bulk single crystal into a desired shape e.g. by cutting or polishing. Accordingly, it is difficult to process cubic zirconia into an optional shape, and cubic zirconia could not be used for an application which requires high design properties, e.g. a complicated shape, or for an application which requires microfabrication.
On the other hand, a translucent zirconia sintered body having high transparency, obtained by molding and firing a zirconia powder, has been reported (Patent Documents 1, 2 and 3 and Non-Patent Document 2). Such a translucent zirconia sintered body can be prepared by molding such as injection molding. Accordingly, a translucent zirconia sintered body can easily be produced as a sintered body having an optional shape. Such a translucent zirconia sintered body having high transparency can be formed into a member having a shape which cannot be achieved by cubic zirconia.
In order to further improve the design properties of a translucent zirconia sintered body, a translucent zirconia sintered body having a rare earth element added as a coloring agent, i.e. a so-called colored translucent zirconia sintered body has been studied (Patent Documents 1 to 3).